With reference to FIG. 1, a conventional plastic automotive cooling fan shroud is shown generally indicated at 10. The shroud 10 is of box shape having a skirt 12 and a motor mount 14 coupled to the skirt by a plurality of arms 16. The skirt 12 is solid and encloses the entire area of a radiator core to which the skirt 12 is mounted.
A number of techniques have been used to improve performance or reduce shroud mass of the conventional shroud. Some suppliers of cooling fan modules remove a shroud skirt entirely and use only a ring shroud and support beams to hold the cooling fan in position behind the radiator. Although this concept results in a shroud of minimum mass, the cooling performance of the fan module is compromised when the vehicle is stationary. Suppliers of fan modules have also provided a box shroud where corners of the shroud are missing or the shroud only covers about half of the radiator core. With this structure, degradation in cooling performance between stationary and highway conditions occurs.
Supplier of fan modules have also attempted to incorporate openings into the shroud skirt which usually have some type of plastic door or rubber flap that will open when acted upon by airflow passing through the heat exchanger at high vehicle speeds. A supplier has also created a cooling fan shroud with elongated openings (no doors) formed in the shape of a nozzle to allow air to pass through easily in one direction but not the other.
Other suppliers have attempted to reduce shroud mass by employing thermoplastic resins with a lower density such as polypropylene. However, the performance of the material is inferior to nylon grades of material at elevated temperatures.
There is a need to provide a low mass fan shroud that does not result in degradation in cooling performance between stationary and highway conditions.